Thyroid UK
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how low is low T3?

Hi all,

I have just been to the Doctor and gotten some inconclusive test results I guess. I am to keep a journal and go back after 2 months.

I went with the symptoms of being extremely tired/fatigued. To the point getting through a normal day is almost impossible. The fatigue is my main concern but other symptoms are there too - I probably wouldn't have linked them all together had I not read about hypothyroidism.

So my results cam back with TSH being normal (1.55 [0.25-5]), Free T4 normal (13.67 [9-20]), Free T3 low (3.67 [4-8.3]).

Now my question is - is 3.67 a lot under? or just under? would that bit under be enough for me to feel symptoms?

My ferritin was in the lower end of normal (36.81 [25-280]) so my Dr suggested I take iron supplement for the next 2 months as well as a multivitamin.

it turns out my LDL Cholesterol is a little up (2.74 [<2.59]) and my HDL cholesterol is low (0.69 [1.04-1.56]) and my BP was up a bit. this surprised me as I eat fairly well. I live in a part of the world with very little access to processed food. I eat fruit and vegetables everyday and wouldn't have a clue what or how to cut anything out without starving :)

If I still have symptoms in 2 months my dr will do more tests - I would ask for antibodies (to check for Hashimoto's).



8 Replies

Oh dear. Your FT3 is very low. It should be around mid-range. Your FT4 is a bit low, too. But, your TSH is low-normal. That sounds very much like central hypo, where the problem lies with the pituitary or the hypothalamus, rather than the thyroid gland itself.

Of course, it is the protocol to go back for a second test, in case the first was a fluke. But, when you do go back, if the TSH is still low-normal, suggest to him that is could be central hypo, and ask for a referral to an endo to get it tested.

You should also ask for your vit D, vit B12 and folate to be tested. Because if your ferritin is low, they are likely to be, too. Whatever you do, do not take a multi-vit, because they are just a waste of money at best, and could be dangerous at worse. You won't get anything much out of them, but they may contain things you don't want. Far better to get tested, and take what you need, in reasonable quantities.

If you're going to take an iron supplement, then take 2000 mg vit C with it, to help absorption, and protect your stomach.

Your cholesterol has nothing to do with what you eat. So, don't bother looking for things you can change. It is high because your T3 is low, and will decrease when your T3 rises (assuming you manage to get treatment). Whatever you do, don't give in to attempts to put you on statins!

So, in answer to your question, yes. Your FT3 is low enough to give you a lot of symptoms. It's low T3 that cause symptoms, because T3 is the active hormone. It's nothing to do with the TSH. And, your test isn't inconclusive at all. That low FT3 means you're hypo. The only trouble is, doctors have no idea what T3 is or what it does!

When you go back for your next test, get and appointment as early in the morning as possible - near 8 am - and fast over-night. That way, your TSH will be at its highest. :)

1 like

Thanks Greygoose.

I really appreciate your reply and insight.

I will ask for the B12, folate and Vit D when I go in February. Unfortunately i can't get a referral to an endo - I live in Tanzania and not many trustworthy doctors (or labs) around. But the doctor I am seeing is pretty good and willing to test what I ask for (and they have their own lab or send to Europe for anything else they can't test for locally).

I'll add the Vitamin C straight away.

Thanks again!


They may be willing to test things, but they don't understand the results, do they. Your FT3 is desperately low, and you should be on thyroid hormone replacement pretty rapidly.


It looks like you are anaemic Ninatz, which is quite common. As suggested ask about your B12 and Vitamin D levels. They normally all go hand in hand. So you might need B12 jabs every three months and 2 vitamin D tabs a day. I have been on all three for years. If anaemic, it can cause tiredness, fatique, heavy bleeding in periods etc.

I would definitely ask to be referred to a Endo, regarding your T3 if it continues to stay low. Knowing the NHS (if you are in the UK) they are very reluctant to discuss the T3 debate because of all the controversy over the T3 drug and the prices the pharmaceutical company charges the NHS. The "Professionals" will argue you the case that the T3 medication does not work, is dangerous blah blah and will not prescribe it especially to new patients. Basically one medication fits all crap.

But even so, it needs to be addressed and rechecked.

Hope this helps :)


Hi Jollydolly,

Thanks for your reply.

So even if I am just in the lower end of the "normal" range for ferritin you'd think I am anaemic? Do you think that's what is giving me the tiredness and not the low T3?

As I explained above I live in Tanzania and have little access to specialist - only when I travel overseas on leave. My current GP is actually 1.5hrs flight away :) But at least I can by any medication needed without prescription!

So I am hoping to be able to work this out with my GP with a testing again in February. She'll test the ferritin, TSH, Free T4 and Free T3 again along with any other tests I suggest.

thanks again!


It's both the low ferritin and the low T3, they both need attention.


Yes I was 39 on my levels when I was tested for ferritin levels. It is best not to take medication prior to testing as suggested, it can give a false reading otherwise. But if you are like me, it is easy to forget that (Generally, If I do not take my thyroxine meds in the morning, I will forget full stop). If on iron supplements, do not take them at the same time as they stop the absorption of the thyroxine, same with the vitamin D. Take the latter two at different intervals and preferably not together.

If rechecking for cholesterol, I have always had to fast prior to testing. But I have always had low readings. So I am ok on that score.

Hope you get better readings next time. :)


Those blood tests don't tell you if you are anaemic or not - you need a full blood count for this. Low ferritin can cause exhaustion like you are describing though as I had low ferritin but was not anaemic and could barely function. I took iron tablets and started to feel much better after 3-4 weeks. Don't bother with a multi-vitamin. Take about 100mg ofiron with 1000mg of vit c a day. I split into two doses. Take both doses on an empty stomach (2hrs after food, 1 hr before) as loads of foods inhibit iron absorption, especially calcium.

Get tested for vit d, Folate and b12 as mentioned above as these can cause exhaustion if low. Also thyroid problems can cause low stomach acid which can stop you absorbing nutrients.

T3 is low - as some people seem to get symptoms wthe in range results and yours are out of range then this could be causing your symptoms. Good advice on this above!


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